/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using Spring.Util;

namespace Spring.Core.IO;

/// <summary>
/// <see cref="IResource"/> adapter implementation for a
/// <see cref="System.IO.Stream"/>.
/// </summary>
/// <remarks>
/// <p>
/// Should only be used if no other <see cref="Spring.Core.IO.IResource"/>
/// implementation is applicable.
/// </p>
/// <p>
/// In contrast to other <see cref="Spring.Core.IO.IResource"/>
/// implementations, this is an adapter for an <i>already opened</i>
/// resource - the <see cref="Spring.Core.IO.InputStreamResource.IsOpen"/>
/// therefore always returns <see langword="true"/>. Do not use this class
/// if you need to keep the resource descriptor somewhere, or if you need
/// to read a stream multiple times.
/// </p>
/// </remarks>
/// <author>Juergen Hoeller</author>
/// <author>Rick Evans (.NET)</author>
public class InputStreamResource : AbstractResource
{
    /// <summary>
    /// Creates a new instance of the
    /// <see cref="Spring.Core.IO.InputStreamResource"/> class.
    /// </summary>
    /// <param name="inputStream">
    /// The input <see cref="System.IO.Stream"/> to use.
    /// </param>
    /// <param name="description">
    /// Where the input <see cref="System.IO.Stream"/> comes from.
    /// </param>
    /// <exception cref="System.ArgumentNullException">
    /// If the supplied <paramref name="inputStream"/> is
    /// <see langword="null"/>.
    /// </exception>
    public InputStreamResource(Stream inputStream, string description)
    {
        AssertUtils.ArgumentNotNull(inputStream, "inputStream");

        _inputStream = inputStream;
        _description = description == null ? string.Empty : description;
    }

    /// <summary>
    /// The input <see cref="System.IO.Stream"/> to use.
    /// </summary>
    /// <exception cref="System.InvalidOperationException">
    /// If the underlying <see cref="System.IO.Stream"/> has already
    /// been read.
    /// </exception>
    public override Stream InputStream
    {
        get
        {
            if (_inputStream == null)
            {
                throw new InvalidOperationException(
                    "InputStream has already been read - " +
                    "do not use InputStreamResource if a stream " +
                    "needs to be read multiple times");
            }

            Stream result = _inputStream;
            _inputStream = null;
            return result;
        }
    }

    /// <summary>
    /// Returns a description for this resource.
    /// </summary>
    /// <value>
    /// A description for this resource.
    /// </value>
    /// <seealso cref="Spring.Core.IO.IResource.Description"/>
    public override string Description
    {
        get { return _description; }
    }

    /// <summary>
    /// This implementation always returns true
    /// </summary>
    public override bool IsOpen
    {
        get { return true; }
    }

    /// <summary>
    /// This implemementation always returns true
    /// </summary>
    public override bool Exists
    {
        get { return true; }
    }

    private Stream _inputStream;
    private string _description;
}
